Unearthing clues of catastrophic earthquakes

'An inviting tale of destruction'

SANTA FE, New Mexico -- The destruction and disappearance of ancient cultures mark the history of human civilization, making for fascinating stories and cautionary tales. The longevity of today’s societies may depend upon separating fact from fiction, and archeologists and seismologists are figuring out how to join forces to do just that with respect to ancient earthquakes, as detailed in new studies presented at the international conference of the Seismological Society of America.

"It's an idea whose time has come, " said Robert Kovach, professor of geophysics at Stanford University and a leading proponent that seismology needs to be included in any framework for understanding what happened to past civilizations. Very large earthquakes may have recurrence rates that exceed 500 years, making it very difficult to assign potential hazard estimates.

Archaeoseismology, a young scientific discipline that studies past earthquakes in the archaeological record, allows scientists to broaden the time window to detect these rare seismic catastrophic events. But archaeological evidence for past earthquakes raises a lot of reservations from seismologists, some of them strongly questioning whether man-made structures can be used as earthquake indicators at all.

Controversy stems from what is seen by some seismologists as haphazard blame placed on earthquakes by archaeologists for inexplicable phenomena on an archaeological site, adding drama to the site’s history. “We need to be wary of circular reasoning” said Tina Niemi, a geologist at the University of Missouri-Kansas City, who noted the temptation to assign evidence to match a preconceived notion that an earthquake may have caused damage.

“We are indeed at a turning point with respect to archaeoseismology -- either earthquake evidence in archaeological sites remains in a world of conjecture and drama or a more objective and quantitative approach gets the upper hand,” said Manuel Sintubin, professor of geodynamics at Katholieke Universiteit Leuven in Belgium.

Earlier this month UNESCO awarded a five-year grant to Sintubin and his colleagues Niemi; Iain Stewart, geologist at University of Plymouth in the United Kingdom; and Erhan Altunel, geologist at the Eskisehir Osmangazi University in Turkey, to support archaeoseismology by broadening the field’s primary focus from the Near East to include the Far East.

“The importance of this effort is to create a long-term, worldwide platform for a broad multidisciplinary discussion on archaeoseismology. Our final objective is to assure that archaeoseismology will be considered as a legitimate and complementary source of seismic-hazard information.”

There is still much to be known about ancient earthquakes. The instrumental record for seismology is short, going back 100 years. The historical seismology record is a much longer, including written documentation such as news accounts and diaries, which vary widely by culture and region. The archeoseismic record serves as the bridge between historical accounts and the paleoseismic record of Earth’s history.